In recent years, image processors, for example, copying machines capable of producing a copy of an original document in original, reduced, or enlarged size are widely used. Such a copying machine easily produces reduced or enlarged copies of the original document by magnifying the image of the document at a desired reduction or magnification rate. The copying machines of this type are thus often used for copying various types of documents, maps, or plans of machines and architecture.
A so-called digital copying machine is widely used as a copying machine of this type. The digital copying machine reads a scanned image of a document by an image pickup element, for example, a CCD (charge coupled device) sensor, stores the image data in an image memory, and outputs the image data, for example, after reducing/enlarging the image. Since the image data of the document is temporarily stored in the image memory, the reduction/enlargement processing is easily performed on the image data.
However, for example, when producing a reduced copy, the conventional digital copying machine merely reduces the size of the entire image. Therefore, for example, when the image of the document is reduced by the reduction processing, the characters in the reduced document become too small or the outlines of the characters become unclear. In other words, reading the characters in the document becomes unavailable, resulting in virtually useless copies. Namely, although the conventional digital copying machine easily processes the image data, it performs poor functions, thereby having a rather low value. Hence, the image processor such as copying machine is desired to have a developed structure capable of preventing characters in a reduced copy from becoming too small or unclear and of increasing the value of the image processor.
When a reproduction of a document is used as an original document, i.e., when a copy is produced from a reproduced image of the original, the image quality would be degraded. If a copy is produced from such a degraded document, the outlines of characters in the document become unclear and can not be read, resulting in a virtually useless copy of the image. Thus, there is a demand for developing an image processor which is capable of preventing the characters in a document from becoming unclear even when the image quality of the document is degraded.